<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    #wrap {
      background: red;
      width: 300px;
      height: 3300px;
      margin: 0 auto;
    }

    #nav {
      height: 10px;
      background: greenyellow;
      position: fixed;
      top: 0;
      left: 0;
      width: 1px;
    }
  </style>
</head>
<body>
  <div id="nav"></div>
  <div id="wrap"></div>
  <script src="./index.js"></script>
</body>
</html>